1. Field of the Invention
The present invention relates to a method for threading a running paper web from a preceding section to a following section of a paper-making or paper-finishing machine. The present invention also relates to a system for threading a running paper web from a preceding section to a following section of a paper-making or paper-finishing machine, which system is fitted in connection with a preceding roll from which the running paper web is passed preferably to a pair of rolls with at least one driven roll.
2. Description of the Related Art
The threading process of a running paper web is well-known in the art and it is currently visually monitored and manually influenced. The threading process is transduced step by step, i.e. from section to section of the paper-making or paper-finishing machine. Between two sections, the threading process is started by providing a threading tail, which is usually cut from one edge zone of the running paper web. Then the threading tail is fed to and through the following section via threading elements, i.e. guiding elements (plates with air jets and/or ropes) or narrow belts. Important for a good runnability is a stable threading tail with certain elected properties, such as width or moisture, before threading and a proper draw of the threading tail to avoid breaks.
As a result of this well-known threading process, the efficiency of each threading process mainly depends on the capability and experience of the executing personnel in the paper mill. Moreover, non perfectly performed threadings can cause significant losses in machine operating speeds and runnabilities. For example, a paper-making machine producing 400 tons per day (tpd), with two breaks per day each lasting on average 20 minutes, causes over one million dollars in efficiency losses per year.
Both a method and a system for monitoring the process of separation of a running paper web in a paper-making machine is described in the U.S. Pat. No. 6,231,722 B1 (WO 98/27275 A1, DE 197 82 179 T1). The running paper web is separated from a roll and passed into a free draw, which is preferably the first draw in the paper-making machine. The factors being automatically monitored in the monitoring system are the draw difference of the web, the actual separation point, the web tension after the separation point, variations in loading pressure and moisture. The disclosed method and system are performed and optimized for a paper web running over the center roll of the press, preferably followed by a free draw of the running paper web, in particular the first free draw of the running paper web. However, the referenced patent is more or less completely silent with respect of the threading process for a running paper web.